The present invention relates to sorters for inspecting transversely-spaced articles as they move along a direction of travel, and separating some of the articles from others according to differences in their physical characteristics. In particular, the invention relates to the sorting of relatively small, granular articles by means of a transverse array of fluid nozzles which selectively direct respective streams of fluid toward selected articles to deflect them from their normal direction of travel.
Sorters for detecting differences in the physical characteristics of transversely-spaced articles, and separating some from others according to such differences as the articles move along a direction of travel, are well known. For example, such sorters are widely used in the food-processing industry for detecting defects in foodstuffs by optical inspection, as shown in U.S. Pat. Nos. 3,872,306, 4,186,836, 4,513,868, 4,520,702, 4,630,736, and 5,085,325. Sorters which sort larger articles such as potatoes or fruit often employ mechanical fingers, plungers, or suction tubes which operate in response to electrical defect signals received from the inspection apparatus to separate defective articles from acceptable ones. Where, however, the articles are smaller, such as beans, peas, coffee, rice, etc., it has been common for such sorters to employ solenoid-actuated transversely-spaced air nozzles for directing quick bursts of air at the defective articles to deflect them from their normal direction of travel and thereby achieve the desired separation of the articles.
The sorting of such smaller articles, particularly at increasingly higher rates of production, introduces difficult requirements with respect to the design of air nozzle separation systems. Small articles which are closely spaced transversely to their direction of travel require a correspondingly closely-spaced transverse array of small nozzles to achieve the required separation. Also, the quickness and accuracy with which the respective nozzles must be activated and deactivated increase as the articles become smaller and/or their speed of travel increases to meet higher production demands. These combined requirements of close transverse nozzle spacing and increasingly quicker and more accurate nozzle response have tended to exceed the capabilities of the currently-known air nozzle separation systems.
A principal reason for the foregoing problem is that the solenoid valves which conventionally are used to control the supply of air to the respective nozzles, in response to defect signals received from the inspection apparatus, are much larger than the nozzles which they control, and such valves therefore consume much more space than do the nozzles themselves. Where close transverse spacing of a large number of nozzles is required (such as 128 nozzles in a 42-inch transverse span), the problem of providing space for an equal number of solenoid valves to control the nozzles becomes a difficult one. This is partially because the solenoid valves need to be in close proximity to the nozzles to minimize the delay between solenoid actuation and emission of the airstream from the nozzle in order to provide quick response. Also, the respective conduit lengths between the solenoid valves and their respective nozzles should be substantially equal so that the air-emission delays are uniform from nozzle to nozzle for accuracy in deflecting articles. In addition, the nozzles should be as close as possible both to the article inspection point and to the path of travel of the articles themselves for purposes of accuracy. These combined requirements are difficult to satisfy in a compatible fashion because of space limitations.
For example, a previous air nozzle separation system marketed by the assignee of the present invention employed a linear transverse alignment of air nozzles on the front of a transversely-extending manifold assembly, with large individual solenoid valves being arranged in transverse rows peripherally around the top, rear and bottom of the manifold, protruding radially therefrom and forming a voluminous structure difficult to position in close proximity to the optical inspection station of the sorter. Moreover, the large mass of each solenoid valve limited the speed of valve actuation.
In an attempt to alleviate the space limitation problem, other previously-known systems have employed multiple transverse rows of solenoid valves located at different distances from the transversely-aligned nozzles with different-length sets of air conduits interstitially interconnecting the respective rows of valves to the aligned nozzles. However, the delay time between solenoid actuation and nozzle emission is both long and nonuniform from nozzle to nozzle, adversely affecting both speed and accuracy.
Alternatively, other previous systems have employed multiple transverse rows of nozzles spaced apart along the direction of travel of the articles, with the transverse spacings of the nozzles of the respective rows being staggered. However, since the respective transverse rows of nozzles are at different distances from the inspection station along the direction of travel, different electrical delay times are needed for actuation of the respective rows of nozzles which adversely affects accuracy. Also, the staggered or interstitial relationship of the nozzles of the respective rows places each transversely adjacent pair of nozzles in different rows. Thus, transversely adjacent nozzle pairs cannot cooperate with each other effectively to deflect articles which may pass transversely between them, because the pair of nozzles cannot simultaneously emit their respective airstreams.